VOLATILES FROM DAMAGED PLANTS AS MAJOR CUES IN LONG-RANGE HOST-SEARCHING BY THE SPECIALIST PARASITOID COTESIA-RUBECULA

The role of volatile stimuli in the long-range host-searching behaviou r of the specialist parasitoid Cotesia rubecula Marshall (Hymenoptera: Braconidae) was studied. Components from the plant-host-complex Bruss els sprouts (Brassica oleracea L. var. gemmifera (DC.) Schulz. cv. 'Ti turel')-Pieris rapae L. (Lepidoptera: Pieridae) were compared for thei r attractiveness in dual choice tests in a windtunnel. Stimuli from ca bbage plants that were mechanically damaged or damaged by P. rapae cat erpillars were more attractive to this parasitoid species than stimuli emitted by the host larvae or their faeces. Parasitoids preferred lea ves from the plant-host-complex over artificially damaged leaves. Unda maged cabbage plants were the least attractive to the foraging females . These results indicate that in-flight searching behaviour of C. rube cula is guided by plant-derived information and that for this speciali st species more reliable and specific host-derived cues play a minor r ole at longer distances.